1. Field of the Invention
An aspect of the present invention relates to an image forming apparatus comprising a paper feeding cassette, and, more particularly, to an image forming apparatus comprising a paper feeding cassette having an improved paper feeding structure.
2. Description of the Related Art
As shown in FIG. 1, a conventional paper feeding cassette 100 mounted at an image forming apparatus such as a printer, a fax, or a multi-operation printer comprises a frame 101, a knock-up plate 110 to tilt about a hinge shaft 111 coupled to the frame 101, an overlap supply preventing part 120 provided in front of a paper supply side of the knock-up plate 110. The knock-up plate 110 is supported by a spring 130, and tilts according to an amount of paper stacked on a top surface of the knock-up plate 110.
A pick-up roller 210 is mounted in front of the paper supply side of the knock-up plate 110 and is supported by a main body (not shown) of the image forming apparatus. The pick-up roller 210 picks up the uppermost paper from among the paper stacked on the knock-up plate 110 by an application of a rotational frictional force and supplies the uppermost paper to an image forming part (not shown) through the overlap supply preventing part 120. The overlap supply preventing part 120 is fixed at the frame 101 such that the overlap supply preventing part 120 creates a predetermined angle with respect to the knock-up plate 110. Also, a frictional pad 121 having a large coefficient of friction is attached to a surface of the overlap supply preventing part 120 to form a frictional surface.
Referring to FIGS. 2A and 2B, in a case in which a plurality of the papers are overlapped and supplied from the knock-up plate 110, the lowermost paper is stopped by the frictional force of the friction pad 121. As a result, only the uppermost paper is supplied to the image forming part.
With the knock-up plate 110 structure tilted and supported on the frame 101, referring to FIG. 2A, in a case in which the paper stacked on the knock-up plate 110 is small, an intermediate angle (θ) becomes small, meanwhile, as referring to FIG. 2B, in case where the paper stacked on the knock-up plate 110 is large, the intermediate angle (θ′) becomes large. As above, if the intermediate angle is changed according to amounts of the loaded paper, the frictional force generated by the friction pad 121 is also changed. In a case in which the frictional force applied to the paper 1 is large, that is, in case of FIG. 2B, feed quality may be deteriorated because the paper 1 may be supplied after being crumpled or undesirably folded at an edge of the paper because the paper 1 is caught at the overlap supply preventing part 120.